The invention relates to the cutting of continuous filamentary tow into staple lengths, and in particular to the cutting of crimped or uncrimped tow into lengths shorter than 1/2 inch.
Cutters for cutting a continuous filamentary tow of man-made fiber, such as polyester, for example, into staple lengths have been heretofore proposed. Exemplary of such proposals are the disclosures of U.S. Pat. No. 3,485,120 issued to Keith on December 23, 1969, U.S. Pat. No. 3,831,481 issued to Van Dorn et. al. on Aug. 27, 1974, and U.S. Pat. No. 3,733,945 issued to Cook on May 22, 1973.
In the Van Doorn et al patent, for example, there is disclosed in FIG. 6 a cutter wheel which comprises a pair of interconnected upper and lower circular plates which are spaced in the direction of the axis of rotation of the wheel. The wheel is provided with a circular array of cutter blades which have their ends mounted in the plates and are oriented parallel to the axis of rotation. These blades have sharpened edges facing radially outwardly and mutually spaced by a distance corresponding to the desired length of cut of the tow. Each blade is reinforced by a support post located immediately therebehind, the posts having their ends connected to the plates and thereby serving to interconnect the plates. The upper plate is rotatably driven, with rotary motion being transmitted therefrom to the lower plate primarily by the support posts. As the reel is rotated, a continuous-length tow is wrapped around the periphery of the cutting edges of the blades. As the radial thickness of the tow buildsup, a pressure roller presses the tow radially inwardly past the blades so that the tow is severed into the desired lengths. The cut tow fibers pass into the wheel and exist via a center opening in the lower plate.
One advantage of such a cutter wheel over previously employed cutters is that the frictional heat generated during the cutting action is reduced to such an extent that the need to moisten the tow prior to cutting is eliminated, as explained in afore-mentioned U.S. Pat. No. 3,485,120. That is, when using prior art cutters in which the blades are moved through the tow, frictional heat tended to fuse together fibers whose melting temperatures are reached during cutting. However, the use of a rotary cutter wheel in which the tow is pushed past a circular row of cutters has so reduced the amount of heat generated, that fusing is no longer a problem.
While such cutting wheels have performed acceptably when cutting tow into lengths longer than about 1/2 inch, problems have been encountered when attempting to cut uncrimped tow into lengths less than 1/2 inch. It has been found that the cut fibers tend to "pack" within the cutter wheel. Eventually, the packed fibers build-up to such an extent that the wheel becomes clogged and further cutting is rendered impossible. Accordingly, the cutter must be shut down and the clog removed. Such a problem has been experienced at low throughput speeds and to a greater extent at high throughput speeds such as 450 fpm tow speed.